1. Field of the Invention
The present invention relates to an image forming apparatus and a control method therefor, a program for implementing the method, and a printing system and, more particularly, to an image forming apparatus and a control method therefor, a program for implementing the method, and a printing system which receive print data created by a host computer through an infrastructure such as a network and perform printing on printing paper.
2. Description of the Related Art
In a printing system in which a printing apparatus receives print data created by a host computer through a network and performs printing, a reduction in TCO (Total Cost of Ownership) including not only the cost for introducing a printing apparatus and system but also the cost of expendable supplies such as printing paper and a colorant typified by toner attracts great attention in recent years in terms of a reduction in office costs or the conservation of the global environment.
Conventional problems in such a printing system include one of that anyone who can access a network can perform printing using a printing apparatus installed in an office. Since printing limitations are imposed on no one, and no trace of printing is left, a user may fail to exercise self-control. Accordingly, an excessive amount of printing is often performed, thus causing an increase in office costs.
Under the circumstances, there is implemented a printing system which performs printing limitation for address information such as an IP address in TCP/IP and manages the number of printed sheets by acquiring a print log.
However, the printing limitation for address information adopts a rough method, i.e., includes imposing printing limitations on an apparatus with a particular IP address, and the printing system is unable to perform detailed management such as limiting of the number of sheets to be printed for a particular user. In management of the number of printed sheets with a print log, it is possible to leave a print log for printout, but an administrator needs to monitor the print log to check whether unauthorized printing has been performed. This increases labor costs and causes a departure from the intention to reduce the TCO. In order to solve this problem, there is proposed a printing system having a user-limiting function which limits printout on a user-by-user basis (see Japanese Laid-Open Patent Publication (Kokai) No. 2003-150336).
As in Japanese Laid-Open Patent Publication (Kokai) No. 2003-216579, there has been a client which adds a digital signature to a print request to detect falsification of the print request and transmits it to a print server. The print server confirms the presence of the digital signature and transmits it to a printing processing unit. The printing server verifies the validity of the digital signature and controls whether to enable printing.
As in Japanese Laid-Open Patent Publication (Kokai) No. 2003-022377, there has been a technique in which a printer receives a license ticket including usage rules indicating the printable number of sheets and analyzes the license ticket. The printer prints the contents with a content ID in accordance with the usage rules.
The above described techniques have the following problems.
1. In a general office, there is often found a manner of operation in which the administrative privileges for a host computer are made available to allow free installation of a printer driver for the purpose of increasing the convenience of users of the host computer and reducing the management costs. However, since user authentication is not performed for print data to be transmitted to a printing apparatus by an authentication server, and no limitations in the printable number of sheets are imposed on the print data with limiting information, printing is performed in accordance with a print request from a user. For this reason, the above-mentioned manner of operation does not contribute to a reduction in the TCO of the office. If a print job reflects limiting information acquired from the authentication server, it is possible to impose printing limitations on the basis of the policy of a system defined in the authentication server. However, this cannot be implemented unless the host computer performs authentication for the authentication server and imposes printing limitations according to predetermined limiting information.
2. It is impossible to determine immediately at the time of execution of a print job whether all pages of the print job can be printed. It is also impossible to impose detailed limitations including printing setting limitations. The determination can be made by determining, from information of the currently remaining printable number of sheets (calculated from the maximum printable number of sheets and the actually printed number of sheets) and the total number of print pages of a print job, whether the number of sheets for the print job falls at or below the limited printable number of sheets. However, it may be impossible to immediately know, at the time of execution of the print job, the total number of print pages of a print job, depending on the specifications for print job creation by an OS (operating system) used by a host computer. To cope with this, there can be considered a method of actually creating all pages set for a print job, confirming the total number of print pages, and then transmitting the print job to a printing apparatus. The start of transmission of a print job, however, is delayed by time corresponding to the number of print pages and data size, and the total throughput decreases. Accordingly, the method is not practical.
3. It is impossible to impose limitations on job settings on the side of a printing apparatus. More specifically, it is impossible to control which setting is enabled for which user.